Rubber composition

ABSTRACT

A rubber composition is provided which comprises 100 parts by weight of ethylene-(meth)-acrylate copolymer rubbers and/or ethylene-(meth)-acrylate-unsaturated glycidyl ester copolymers, 5 to 300 parts by weight of a hydroxide of a typical metallic element belonging to Group II or III of the Mendeleev&#39;s periodic table and 0.1 to 50 parts by weight of a metallic acrylate compound. This composition keeps properties required for rubbers such as tensile strength, elasticity, scorch resistance and processability at high levels and is excellent in wear resistance and flame retardance.

This is a division of application Ser. No. 08/052,742, filed Apr. 27,1993.

The present invention relates to a rubber composition and in particular,to a rubber composition which keeps at high levels variouscharacteristics required for rubbers, such as tensile strength,elasticity, scorch resistance and processability and is excellent inwear resistance and flame retardance.

It is known to improve flame retardance of rubber compositions by addinga hydroxide of magnesium or aluminum. However, there has not yet beenprovided a rubber composition which keeps various characteristicsrequired for rubbers, such as tensile strength, elasticity, scorchresistance and processability at high levels and is excellent in wearresistance and flame retardance.

The object of the present invention is to provide a rubber compositionwhich keeps at high levels various characteristics required for rubbers,such as tensile strength, elasticity, scorch resistance andprocessability and is excellent in wear resistance and flame retardance.

After intensive research, the inventors have accomplished the presentinvention.

One of the present invention relates to a rubber composition comprising100 parts by weight of the following component (A), 5 to 300 parts byweight of the following component (B) and 0.1 to 50 parts by weight ofthe following component (C).

Component (A): Ethylene-acrylate or methacrylate (herein referred to"(meth)acrylate") copolymer rubbers and/orethylene-(meth)acrylate-unsaturated glycidyl ester copolymer rubbers.

Component (B): Hydroxides of typical metal elements belonging to GroupII or III of the Mendeleev's periodic table.

Component (C): At least one metallic acrylate compound represented bythe following formula (I): ##STR1## (wherein R represents a hydrogenatom or an alkyl group of 1 to 8 carbon atoms, M represents a mono- totri-valent metallic atom, m represents an integer of 1 to 3 and nrepresents an integer of 0 to 2).

Another invention relates to a rubber composition comprising 100 partsby weight of the above component (A), 5 to 300 parts by weight of theabove component (B) and 2 to 100 parts by weight of the followingcomponent (D).

Component (D): Ethylene copolymers containing carboxylic acids or acidanhydrides.

Still another invention relates to a rubber composition comprising 100parts by weight of the above component (A), 5 to 300 parts by weight ofthe above component (B), 0.1 to 50 parts by weight of the abovecomponent (C) and 2 to 100 parts by weight of the above component (D).

The present invention will be explained in detail.

The component (A) comprises ethylene-(meth)-acrylate copolymer rubbersand/or ethylene-(meth)-acrylate-unsaturated glycidyl ester copolymerrubbers. The (meth)acrylate means an acrylate or a methacrylate. The(meth)acrylates are preferably those which are obtained from alcohols of1-8 carbon atoms. Examples are methyl acrylate, methyl methacrylate,ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butylmethacrylate, tert-butyl acrylate, tert-butyl methacrylate, 2-ethylhexylacrylate and 2-ethylhexyl methacrylate. These may be used each alone orin combination of two or more.

Ratio (molar ratio) of ethylene to (meth)acrylate in theethylene-(meth)acrylate copolymer rubbers is preferably (50 to 85):(50to 15), more preferably (58 to 80):(42 to 20). If amount of the(meth)acrylate is too large, brittle point of the copolymer is high andproperties as rubbers (elastomers) in low-temperature atmosphere aresometimes inferior. If it is too small, crystallinity of the copolymeris high and a sufficient elasticity for elastomer is not obtained insome case.

Examples of the unsaturated glycidyl esters are glycidyl acrylate,glycidyl methacrylate, diglycidyl itaconate, triglycidylbutenetricarboxylate and glycidyl p-styrenecarboxylate. With referenceto the proportion of the unsaturated glycidyl ester in theethylene-(meth)acrylate-unsaturated glycidyl ester copolymers, the molarratio of (ethylene+(meth)acrylate):(unsaturated glycidyl ester) ispreferably 1: (0.0005 to 0.05), more preferably 1:(0.001 to 0.03). Whencopolymer rubbers containing the unsaturated glycidyl ester in an amountof the above range are used, it becomes possible to vulcanize them withvarious vulcanizers utilizing the epoxy group of the glycidyl ester.Copolymer rubbers having no unsaturated glycidyl ester are able to bevulcanized with organic peroxides.

As the component (A), in addition to those which comprise ethylene and(meth)acrylate or comprise ethylene, (meth)acrylate and unsaturatedglycidyl ester, there may be used copolymers comprising other units inaddition to the above units so long as advantageous effects of thepresent invention are not damaged. Other units include, for example,isobutylene, styrene and derivatives thereof, vinyl acetate, andhalogenated olefins such as tetrafluoroethylene and hexafluoropropylene.Preferred are those which have a melt index at 190° C. specified in JISK6791 of 0.5 to 500 g/10 min. and more preferred are those which havethe melt index of 0.5 to 50 g/10 min. If the melt index is too large,strength of the copolymers is insufficient and rubber elasticity isinferior. If the melt index is too small, processability of thecopolymers is inferior.

The ethylene-(meth)acrylate copolymer rubbers or theethylene-(meth)acrylate-unsaturated glycidyl ester copolymer rubbers areobtained by known polymerization methods such as free-radical initiatedbulk polymerization, emulsion polymerization and solutionpolymerization. As an example, mention may be made of the methodmentioned in Japanese Patent Kokoku No. 46-45085, namely, the method ofpreparation under a pressure of 500 kg/cm² or higher and a temperatureof 40 to 300° C. in the presence of a polymerization initiator whichproduces free radicals.

The component (B) comprises hydroxides of typical metallic elementsbelonging to Group II or III of the Mendeleev's periodic table. Examplesare magnesium hydroxide and aluminum hydroxide. These may be used eachalone or in combination of two or more.

The component (C) comprises at least one metallic acrylate compoundrepresented by the above formula (I). In the formula, R represents ahydrogen atom or an alkyl group of 1 to 8 carbon atoms, preferably ahydrogen atom or a methyl group, M represents a mono- to tri-valentmetallic atom, m represents an integer of 1 to 3 and n represents aninteger of 0 to 2. Examples of M are lithium, sodium, potassium,magnesium, calcium, strontium, barium, manganese, iron, cobalt, nickel,copper, silver, zinc and aluminum. Examples of the metallic acrylatecompounds are zinc acrylate, magnesium acrylate, aluminumhydroxyacrylate, zinc methacrylate, magnesium methacrylate and aluminumhydroxymethacrylate. These may be used each alone or in combination oftwo or more. Furthermore, metallic polyacrylates may also be used as thecompound represented by the formula (I).

The component (D) comprises ethylene copolymers containing carboxylicacids or acid anhydrides. Examples of the ethylene copolymers containingcarboxylic acids or acid anhydrides are ethylene-maleic anhydridecopolymer, ethylene-acrylate-maleic anhydride copolymer andethylene-acrylate-maleic anhydride half ester copolymer. Theethylene-maleic anhydride copolymer may be a copolymer obtained byradical polymerization of ethylene and maleic anhydride under highpressures and a copolymer containing a radical copolymerizable monomersuch as vinyl acetate, methyl methacrylate, ethyl acrylate or butylacrylate in addition to ethylene and maleic anhydride.

The rubber composition of the present invention comprises components(A), (B) and (C), components (A), (B) and (D) or components (A), (B),(C) and (D).

Content of the component (B) is in the range of 5 to 300 parts byweight, preferably 10 to 200 parts by weight every 100 parts by weightof the component (A). If the content is too small, the composition isinferior in flame retardance and if it is too large, the composition isinferior in processability.

Content of the component (C) in the rubber compositions comprisingcomponents (A), (B) and (C) is in the range of 0.1 to 50 parts byweight, preferably 0.5 to 20 parts by weight every 100 parts by weightof the component (A). If the content is too small, the composition isinferior in wear resistance and if it is too large, the composition isinferior in processability.

Content of the component (D) in the rubber compositions comprisingcomponents (A), (B) and (D) is in the range of 2 to 100 parts by weight,preferably 5 to 50 parts by weight every 100 parts by weight of thecomponent (A). If the content is too small, the composition is inferiorin wear resistance and if it is too large, the composition is inferiorin rubber elasticity and scorch resistance.

The rubber compositions of the present invention may comprise 100 partsby weight of the component (A), 5 to 300 parts by weight, preferably 10to 200 parts by weight of the component (B), 0.1 to 50 parts by weight,preferably 0.5 to 20 parts by weight of the component (C) and 2 to 100parts by weight, preferably 5 to 50 parts by weight of the component(D). When the rubber compositions contain all of the components (A),(B), (C) and (D) as above, wear resistance and tensile strength arefurther conspicuously improved.

Two or more ingredients in each of the components (A) to (D) may be usedin combination. In this case, the total amount of them in each componentmust satisfy the range of the content of the component.

Method for production of the rubber compositions of the presentinvention and method for use thereof are as follows. The respectivecomponents and, if necessary, carbon black, organic peroxides,anti-oxidants, vulcanizing accelerators, processing aids, stearic acid,reinforcing agents, fillers, plasticizers, softening agents and othersare mixed by usual kneaders such as roll mills and Banbury mixer to makea vulcanizable rubber composition. The resulting rubber composition ismolded into a desired shape and subjected to vulcanization to make avulcanized rubber composition which is a molded final article. Thevulcanization is usually carried out at a temperature of 120° C. orhigher, preferably 150° to 220° C. for about 1 to 30 minutes.

When copolymer rubbers having unsaturated glycidyl esters are used ascomponent (A), the epoxy group is able to be a crosslinking site.Examples of the vulcanizers reactable with the epoxy group arecombinations of quaternary ammonium salts, quaternary phosphonium saltsand organic phosphorus compounds with organic acids and polyfunctionalamine compounds.

As the organic peroxides, there may be used those which are generallyused for crosslinking of rubbers. Examples of the organic peroxides aredi-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α,α-bis(t-butylperoxyisopropyl)benzene,2,5-dimethyl-2,5-di(t-butylperoxy)hexane,2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3,1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,n-butyl-4,4-bis(t-butylperoxy)valerate, 2,2-bis(t-butylperoxy)butane and2,2-bis(t-butylperoxy)octane.

Amount of the organic peroxide is preferably in the range of 1 to 10parts by weight, more preferably in the range of 2 to 6 parts by weightevery 100 parts by weight of the copolymer. If the amount is too small,crosslinking density is low and mechanical strength of the vulcanizedrubber compositions is insufficient. If it is too large, problems suchas blowing often occur at the time of vulcanization and molding.Furthermore, known crosslinking aids such as p,p'-dibenzoylquinonedioxime, quinone dioxime, triallyl cyanurate, sulfur, ethylenedimethacrylate, N,N'-m-phenylenebismaleimide, triallyl isocyanurate andtrimethylolpropane trimethacrylate may be used for improvingcrosslinking efficiency in vulcanization with organic peroxides.

The rubber compositions of the present invention are able to be used ina wide field taking advantage of the excellent properties. Especially,they are suitable as covering materials for electric wires and cablesused in multistory buildings, power stations, ships and various plants.

The present invention will be explained by the following Examples andComparative Examples.

Examples 1-18 and Comparative Examples 1-5

The components shown in Table 1 (excluding peroxide and triallylisocyanurate) were kneaded with a Brabender plastomill of 350 ccadjusted to 90° C. at a rotor velocity of 60 rpm for 5 minutes.Thereafter, peroxide and triallyl isocyanurate were added thereto andkneaded with an open roll mill of 6 inches to obtain a rubbercomposition. Then, the rubber composition was press vulcanized to obtaina vulcanized rubber. This vulcanized rubber was evaluated on propertiesin accordance with JIS K6301 except for the annotated properties.

Measurement of abrasion wear was conducted in the following manner. Thatis, the sample vulcanized rubber was subjected to preliminary abrasionof 500 times using a Taber machine (using a whetstone of H-18 and a loadof 500 g) and was further subjected to abrasion of 1000 times andthereafter weight change of the sample was measured and the decrement inweight was taken as abrasion wear. The measurement was carried out 3times and the average value was used for evaluation. Measurement ofoxygen index (O.I.) was conducted in accordance with JIS K7201.

Results of the all evaluations are shown in Table 1.

From the results, the following are recognized.

That is, all of the Examples of the present invention show satisfactoryresults of evaluations. On the other hand, the samples of ComparativeExamples 1-4 in which neither the component (C) nor the component (D) ofthe present invention were used were infrior in wear resistance. Thesample of Comparative Example 2 was further inferior in tensilestrength. Considerable scorching occurred in Comparative Example 5 wherethe component (A) was not used.

                                      TABLE 1                                     __________________________________________________________________________    Components *1                                                                 (Part by Example                                                                             Example                                                                             Example                                                                             Example                                                                             Example                                      weight)  1     2     3     4     5                                            __________________________________________________________________________    Component (A)                                                                 Kind *2  A1    A1    A1    A1    A1                                           Amount   100   100   100   100   100                                          Component (B) *3                                                                       100   100   100   100   100                                          Component (C)                                                                 C1 *4    1     3     0     0     0                                            C2       0     0     0     0     0                                            Component (D)                                                                 Kind *5  --    --    D1    D1    D1                                           Amount   0     0     5     10    20                                           LDPE *6  0     0     0     0     0                                            Evaluation                                                                    Mooney scorch                                                                 125° C.                                                                Vm       16.3  18.5  13.4  15.7  21.2                                         t5 minute                                                                              14.3  11.0  27.6  30.0  30.8                                         t35 minute                                                                             52.1  17.0  >60   >60   >60                                          Properties of                                                                 vulcanized                                                                    product *7                                                                    Tensile strength                                                                       68    107   68    75    86                                           Kgf/cm.sup.2                                                                  Elongation                                                                             310   210   390   390   370                                          Hardness JIS-A                                                                         74    79    72    76    81                                           Taber abrasion                                                                         0.3031                                                                              0.2278                                                                              0.5297                                                                              0.4791                                                                              0.3578                                       wear                                                                          g/1000 times                                                                  Oxygen index                                                                           30.0  30.0              28.0                                         (O.I.)                                                                        __________________________________________________________________________    Components *1                                                                 (Part by Example                                                                             Example                                                                             Example                                                                             Example                                                                             Example                                      weight)  6     7     8     9     10                                           __________________________________________________________________________    Component (A)                                                                 Kind *2  A1    A1    A1    A1    A1                                           Amount   100   100   100   100   100                                          Component (B) *3                                                                       100   100   100   100   100                                          Component (C)                                                                 C1 *4    0     0     0     0     0                                            C2       0     0     0     0     0                                            Component (D)                                                                 Kind *5  D2    D2    D2    D3    D3                                           Amount   5     10    20    10    20                                           LDPE *6  0     0     0     0     0                                            Evaluation                                                                    Mooney scorch                                                                 125° C.                                                                Vm       11.7  12.9  18.9  15.9  17.9                                         t5 minute                                                                              24.0  25.8  28.1  17.2  18.9                                         t35 minute                                                                             >60   >60   >60   45.5  45.9                                         Properties of                                                                 vulcanized                                                                    product *7                                                                    Tensile strength                                                                       72    71    75    80    86                                           Kgf/cm.sup.2                                                                  Elongation                                                                             430   400   410   320   330                                          Hardness JIS-A                                                                         70    72    73    71    72                                           Taber abrasion                                                                         0.5127                                                                              0.4780                                                                              0.3977                                                                              0.3910                                                                              0.2807                                       wear                                                                          g/1000 times                                                                  Oxygen index         28.0                                                     (O.I.)                                                                        __________________________________________________________________________    Components *1                                                                 (Part by Example                                                                             Example                                                                             Example                                                                             Example                                                                             Example                                      weight)  11    12    13    14    15                                           __________________________________________________________________________    Component (A)                                                                 Kind *2  A2    A1    A1    A1    A1                                           Amount   100   100   100   100   100                                          Component (B) *3                                                                       100   100   100   100   100                                          Component (C)                                                                 C1 *4    0     1     2     3     0                                            C2       0     0     0     0     3                                            Component (D)                                                                 Kind *5  D1    D1    D1    D1    D3                                           Amount   10    20    20    20    20                                           LDPE *6  0     0     0     0     0                                            Evaluation                                                                    Mooney scorch                                                                 125° C.                                                                Vm       18.0  24.9  25.1  27.2  22.2                                         t5 minute                                                                              14.2  21.4  13.0  15.0  23.2                                         t35 minute                                                                             50.7  >60   39.5  24.5  >60                                          Properties of                                                                 vulcanized                                                                    product *7                                                                    Tensile strength                                                                       70    97    112   126   87                                           Kgf/ cm.sup.2                                                                 Elongation                                                                             340   280   220   210   330                                          Hardness JIS-A                                                                         75    81    82    84    81                                           Taber abrasion                                                                         0.4152                                                                              0.2504                                                                              0.1904                                                                              0.2109                                                                              0.2343                                       wear                                                                          g/1000 times                                                                  Oxygen index         28.0  28.0                                               (O.I.)                                                                        __________________________________________________________________________    Components *1                                                                 (Part by Example                                                                             Example                                                                             Example                                                                             Example                                            weight)  16    17    18    19                                                 __________________________________________________________________________    Component (A)                                                                 Kind *2  A1    A1    A1    A2                                                 Amount   100   100   100   100                                                Component (B) *3                                                                       100   100   100   100                                                Component (C)                                                                 C1 *4    0     0     1     1                                                  C2       4     5     3     3                                                  Component (D)                                                                 Kind *5  D1    D1    D1    D1                                                 Amount   20    20    20    20                                                 LDPE *6  0     0     0     0                                                  Evaluation                                                                    Mooney scorch                                                                 125° C.                                                                Vm       23.2  24.5  23.1  31.8                                               t5 minute                                                                              23.1  21.3  13.8  8.1                                                t35 minute                                                                             >60   >60   54.5  39.8                                               Properties of                                                                 vulcanized                                                                    product *7                                                                    Tensile strength                                                                       89    94    102   96                                                 Kgf/cm.sup.2                                                                  Elongation                                                                             290   270   270   260                                                Hardness JIS-A                                                                         82    83    82    80                                                 Taber abrasion                                                                         0.2340                                                                              0.2497                                                                              0.2098                                                                              0.2324                                             wear                                                                          g/1000 times                                                                  Oxygen index   28.0  28.0  28.0                                               (O.I.)                                                                        __________________________________________________________________________             Compara-                                                                            Compara-                                                                            Compara-                                                                            Compara-                                                                            Compara-                                     Components *1                                                                          tive  tive  tive  tive  tive                                         (Part by example                                                                             example                                                                             example                                                                             example                                                                             example                                      weight)  1     2     3     4     5                                            __________________________________________________________________________    Component (A)                                                                 Kind *2  A1    A2    A1    A1    --                                           Amount   100   100   100   100   0                                            Component (B) *3                                                                       100   100   100   100   100                                          Component (C)                                                                 C1 *4    0     0     0     0     0                                            C2       0     0     0     0     0                                            Component (D)                                                                 Kind *5  --    --    --    --    D3                                           Amount   0     0     0     0     100                                          LDPE *6  0     0     5     10    0                                            Evaluation                                                                    Mooney scorch                                                                 125° C.                                                                Vm       8.6   19.5  11.7  10.9                                               t5 minute                                                                              26.0  21.5  30.2  28.1  *8                                           t35 minute                                                                             >60   >60   >60   >60   Measur-                                      Properties of                    ement                                        vulcanized                       was                                          product *7                       impos-                                       Tensile strength                                                                       70    64    76    69    sible.                                       Kgf/cm.sup.2                                                                  Elongation                                                                             380   440   410   390                                                Hardness JIS-A                                                                         65    61    72    73                                                 Taber abrasion                                                                         0.5937                                                                              0.5321                                                                              0.6044                                                                              0.5863                                             wear                                                                          g/1000 times                                                                  Oxygen index                                                                           30                                                                   (O.I.)                                                                        __________________________________________________________________________     *1 Components                                                                 The following common components were used in addition to those shown in       Table 1: 15 parts by weight of SEAST SO (FEF carbon black manufactured by     Tokai Carbon Co.); 1 part by weight of stearic acid; 1 part by weight of      stearylamine (0.5 part by weight in Examples 3 to 11 and Comparative          Examples 1 to 5); 2 parts by weight of NOGUARD 445 (aging inhibitor           manufactured by Uniroyal Co.); 8.8 parts by weight of DCP40 (dicumyl          peroxide manufactured by Nippon Oil & Fats Co., Ltd.); and 1 part by          weight of triallyl isocyanurate.                                              *2 Component (A)                                                              A1: Ethylene (66.3 mol %)methyl acrylate (33.0 mol %)glycidyl methacrylat     (0.7 mol %) copolymer rubber.                                                 A2: Ethylene (67.0 mol %)methyl acrylate (33.0 mol %) copolymer rubber.       *3 Component (B)                                                              KISUMA 5B (magnesium hydroxide manufactured by Kyowa Chemical Co.)            *4 Component (C)                                                              C1: Compound of the formula (1) where R =  hydrogen atom, M = Zn, m = 2,      and n = 0 (zinc acrylate).                                                    C2: Compound of the formula (1) where R = hydrogen atom, M = A1, m = 2,       and n = 1 (aluminum acrylate).                                                *5 Component (D)                                                              D1: BONDINE TX8030 [Ethylene (85.0% by weight)maleic anhydride (3.5% by       weight)ethyl acrylate (11.5% by weight) copolymer having a melting point      of 95° C. and an MFR (190° C.) of 3.0 g/10 min and              manufactured by Sumitomo Chemical Co.,                                        D2: BONDINE TX8390 [Ethylene (68% by weight)maleic anhydride (2% by           weight)ethyl acrylate (30% by weight) copolymer having a melting point of     67° C. and an MFR (190° C.) of 7.0 g/10 min and manufacture     by Sumitomo Chemical Co., Ltd.                                                D3: VamacG (Ethylenemethyl acrylatemaleic anhydride half ester copolymer      manufactured by DuPont Co.)                                                   *6 LDPE                                                                       SUMIKASEN F7023 (Lowdensity polyethylene having a melting point of            107° C. and an MFR (190° C.) of 6.7 g/10 min and                manufactured by Sumitomo Chemical Co., Ltd.)                                  *7 Properties of vulcanized products                                          Properties of products vulcanized at 170° C. for 20 minutes.           *8 Scorch occurred and measurement of the properties was impossible.     

As explained above, the present invention provides a rubber compositionwhich keeps various properties required for rubbers such as tensilestrength, elasticity, scorch resistance and processability at highlevels and is excellent in wear resistance and flame retardance.

We claim:
 1. A rubber composition which comprises 100 parts by weight ofthe following component (A), 10 to 200 parts by weight of the followingcomponent (B) and 5 to 50 parts by weight of the following component(D):component (A): a copolymer rubber selected from the group consistingof ethylene-(meth)acrylate copolymer rubbers andethylene-(meth)acrylate-unsaturated glycidyl ester copolymer rubbers,wherein the molar ratio of ethylene to (meth)acrylate in theethylene-(meth)acrylate copolymer rubbers is from 50/50 to 85-15, andthe molar ratio of (ethylene+(meth)acrylate) to unsaturated glycidylester in the ethylene-(meth)acrylate-unsaturated glycidyl estercopolymer rubbers is from 1/0.0005 to 1/0.05, component (B): a hydroxideof a metallic element belonging to Group II or III of Mendeleev'speriodic table, and component (D): an ethylene copolymer containing acarboxylic acid or an acid anhydride.
 2. A rubber composition accordingto claim 1, wherein the (meth)acrylate is obtained from an alcohol of 1to 8 carbon atoms.
 3. A rubber composition according to claim 1, whereinthe (meth)acrylate is methyl acrylate, methyl methacrylate, ethylacrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate,tert-butyl acrylate, tert-butyl methacrylate, 2-ethylhexyl acrylate or2-ethylhexyl methacrylate.
 4. A rubber composition according to claim 1,wherein molar ratio of ethylene and (meth)acrylate in theethylene-(meth)acrylate copolymer rubber is 50 to 85:50 to
 15. 5. Arubber composition according to claim 1, wherein molar ratio of ethyleneand (meth)acrylate in the ethylene-(meth)acrylate copolymer rubber is 58to 80:42 to
 20. 6. A rubber composition according to claim 1, whereinthe unsaturated glycidyl ester is glycidyl acrylate, glycidylmethacrylate, diglycidyl itaconate, triglycidyl butenetricarboxylate orglycidyl p-styrene-carboxylate.
 7. A rubber composition according toclaim 1, wherein molar ratio of ethylene+(meth)acrylate: unsaturatedglycidyl ester in the ethylene-(meth)-acrylate-unsaturated glycidylester copolymer is 1:0.0005 to 0.05.
 8. A rubber composition accordingto claim 1, wherein molar ratio of ethylene+(meth)acrylate: unsaturatedglycidyl ester in the ethylene-(meth)-acrylate-unsaturated glycidylester copolymer is 1:0.001 to 0.03.
 9. A rubber composition according toclaim 1, wherein the component (A) has a melt index at 190° C.specificed in JIS K6791 of 0.5 to 500 g/10 min.
 10. A rubber compositionaccording to claim 1, wherein the component (A) has a melt index at 190°C. specificed in JIS K6791 of 0.5 to 50 g/10 min.
 11. A rubbercomposition according to claim 1, wherein the component (B) is magnesiumhydroxide or aluminum hydroxide.
 12. A rubber composition according toclaim 1, wherein the component (D) is ethylene-maleic anhydridecopolymer, ethylene-acrylate-maleic anhydride copolymer orethylene-acrylate-maleic anhydride half ester copolymer.
 13. A rubbercomposition according to claim 1, wherein content of the component (B)is in the range of 10 to 200 parts by weight per 100 parts by weight ofthe component (A).
 14. A rubber composition according to claim 1,wherein content of the component (D) is in the range of 5 to 50 parts byweight per 100 parts by weight of the component (A).
 15. A coveringmaterial for electric wires or cables which comprises the rubbercomposition of claim
 1. 16. A rubber composition which comprises 100parts by weight of the following component (A), 10 to 200 parts byweight of the following component (B), 0.5 to 20 parts by weight of thefollowing component (C) and 5 to 50 parts by weight of the followingcomponent (D):component (A): at least one of ethylene-(meth)acrylatecopolymer rubbers and ethylene-(meth)acrylate-unsaturated glycidyl estercopolymers, component (B): a hydroxide of a metallic element belongingto Group II or III of Mendeleev's periodic table, component (C): atleast one metallic acrylate compound represented by the followingformula (I): ##STR2## wherein R represents a hydrogen atom or an alkylgroup of 1 to 8 carbon atoms, M represents a mono- to tri-valent metalatom, m represents an integer of 1 to 3 and n represents an integer of 0to
 2. component (D): an ethylene copolymer containing a carboxylic acidor an acid anhydride.
 17. A rubber composition according to claim 16,wherein the (meth)acrylate is obtained from an alcohol of 1 to 8 carbonatoms.
 18. A rubber composition according to claim 16, wherein the(meth)acrylate is methyl acrylate, methyl methacrylate, ethyl acrylate,ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, tert-butylacrylate, tert-butyl methacrylate, 2-ethylhexyl acrylate or 2-ethylhexylmethacrylate.
 19. A rubber composition according to claim 16, whereinmolar ratio of ethylene and (meth)acrylate in theethylene-(meth)acrylate copolymer rubber is 50 to 85:50 to
 15. 20. Arubber composition according to claim 16, wherein molar ratio ofethylene and (meth)acrylate in the ethylene-(meth)acrylate copolymerrubber is 58 to 80:42 to
 20. 21. A rubber composition according to claim16, wherein the unsaturated glycidyl ester is glycidyl acrylate,glycidyl methacrylate, diglycidyl itaconate, triglycidylbutenetricarboxylate or glycidyl p-styrene-carboxylate.
 22. A rubbercomposition according to claim 16, wherein molar ratio ofethylene+(meth)acrylate: unsaturated glycidyl ester in theethylene-(meth)-acrylate-unsaturated glycidyl ester copolymer is1:0.0005 to 0.05.
 23. A rubber composition according to claim 16,wherein molar ratio of ethylene+(meth)acrylate: unsaturated glycidylester in the ethylene-(meth)-acrylate-unsaturated glycidyl estercopolymer is 1:0.001 to 0.03.
 24. A rubber composition according toclaim 16, wherein the component (A) has a melt index at 190° C.specificed in JIS K6791 of 0.5 to 500 g/10 min.
 25. A rubber compositionaccording to claim 16, wherein the component (A) has a melt index at190° C. specificed in JIS K6791 of 0.5 to 50 g/10 min.
 26. A rubbercomposition according to claim 16, wherein the component (B) ismagnesium hydroxide or aluminum hydroxide.
 27. A rubber compositionaccording to claim 16, wherein the component (C) has the formula (I)where M is lithium, sodium, potassium, magnesium, calcium, strontium,barium, manganese, iron, cobalt, nickel, copper, silver, zinc oraluminum.
 28. A rubber composition according to claim 16, wherein thecomponent (C) is zinc acrylate, magnesium acrylate, aluminumhydroxyacrylate, zinc methacrylate, magnesium methacrylate or aluminumhydroxymethacrylate.
 29. A rubber composition according to claim 16,wherein the component (D) is ethylene-maleic anhydride copolymer,ethylene-acrylate-maleic anhydride copolymer or ethylene-acrylate-maleicanhydride half ester copolymer.
 30. A rubber composition according toclaim 16, wherein content of the component (B) is in the range of 10 to200 parts by weight per 100 parts by weight of the component (A).
 31. Arubber composition according to claim 16, wherein content of thecomponent (C) is in the range of 0.5 to 20 parts by weight per 100 partsby weight of the component (A).
 32. A rubber composition according toclaim 16, wherein content of the component (D) is in the range of 5 to50 parts by weight per 100 parts by weight of the component (A).
 33. Arubber composition according to claim 16 which comprises 100 parts byweight of the component (A), 10 to 200 parts by weight of the component(B), 0.5 to 20 parts by weight of the component (C) and 5 to 50 parts byweight of the component (D).
 34. A covering material for electric wiresor cables which comprises the rubber composition of claim 16.